In order for a shoe to fit properly, it should not only be of the correct length, but also should have inside width and girth dimensions that substantially continually match those of the foot therein. As used herein, girth is defined as the transverse circumference around the foot, typically measured at the ball, waist and instep thereof, and is also used to describe the effective inside circumference of the shoe in the same regions. In conventional footwear, such proper fit is approached only by offering a full range of some nine or more successively graduated width increments for each size in length. However, even with such full width ranges, some means of further girth adjustment is still needed to accommodate differences between left and right foot girths as well as those caused by diurnal and other girth variations experienced by the foot, which variations, primarily due to fluid accumulation in the foot, usually amount to up one and one half or even two full width sizes in range. Despite this well known information, the economics of mass production and distribution have brought about the widespread practice of limiting most shoe offerings to a single width for each size in length, resulting in only an approximate and usually poor fit in most cases, often resulting in serious foot disorders over time.
For these reasons, there has been a continuing need for a practical and economical shoe construction affording width and girth adjustment through means that are relatively concealed to allow such adjustability to be applied to a wide variety of shoe styles including those with conventional bottoms and attachment of uppers thereto.
Adjustable girth footwear is not new; much prior art has employed visible means of girth adjustment including laces, straps and the like, most of which are rarely adaptable to girth adjustment at the ball of the foot, where such adjustment is most needed. Moreover, these means are not even present in styles having typically no such girth adjustment means, such as loafers, women's dress shoes of various heel heights, and many other casual and boot styles; in addition, there are well-defined needs for footwear having means of girth adjustment that are automatic, not only to prevent improper manual adjustment, but to provide such adjustment to those who might otherwise have difficulty with other manual means, as for example, young children, the handicapped, and the elderly.
Adjustable girth footwear are also disclosed in U.S. Pat. Nos. 3,404,468, 3,541,708, and 3,686,777 granted this inventor. None of these proved marketable for several reasons: the latter patents were too complex to be able to be produced competitively, and were prone to malfunction as a result of dirt entrapment in the mechanism, while he embodiments of '468 suffered from similar problems, as well as durability and appearance compared to conventional shoes, and finally, the last three figures of '468 (11 through 13) failed to give sufficient girth adjustment to be worth consideration. However, despite their many shortcomings, they did serve to suggest the merit of the considerable added R&D that has led finally to the present invention.
U.S. Pat. Nos. 3,442,031 and 3,922,800 disclose shoes in which the girth is adjusted by raising at least part of the top surface of the insole, thereby not only changing the shoe's girth but the elevation of a foot in the shoe as well. Since, as a practical matter, such adjustment would usually take place in the forepart of the shoe to preserve a comfortable fit in the counter and backpart, there results an imbalanced adjustment that can change the effective `tread` of the shoe, i.e. the relationship of the height of the wearer's heel to that of the ball. Moreover since proper adjustment of girth normally reflects the usual girth difference between left and right foot, another result would often be to have a person's feet at essentially different heights above the walking surface, which could over time result in serious orthopedic problems.
U.S. Pat. Nos. 490,998; 2,691,227 and 3,436,842, while apparently having some similarity to this invention are actually quite different in function, providing a measure of girth adjustment only when the shoe is unweighted while the present invention provides girth adjustment in both unweighted and weightbearing conditions, the latter being considered as far more important as the discomfort and trauma experienced with ill-fitting shoes occurs mainly under weight-bearing conditions. Furthermore, the latter two patents disclose no means to prevent entrapment of dirt and pebbles within the described structure.
U.S. Pat. No. 3,693,270 uses deformable sponges that are secured to the inside of a boot primarily to facilitate insertion and removal of the foot without the use of a zipper or other enlarging means. However, the heat and pressure build-up experienced with such inserts, particularly those worn over the foot in the ball area, has precluded their use in conventional dress and casual footwear.
U.S. Pat. No. 4,736,531 describes a shoe with a partial elastic slipper sock surrounding the forepart of the foot and fastened to the bottom assembly, free of attachment to the upper. While this structure may limit tongue misalignment in use, it affords no substantial girth adjustment as the narrower foot in such a shoe would typically experience looseness and resultant buckling when weight bearing during the stride cycle over the sensitive top area of the ball of the foot, where the foot flexes in motion.
U.S. Pat. No. 4,038,762 discloses use of viscous flowable materials within closures, primarily for use in alpine ski boots having rigid soles, and as described, is not applicable to conventional footwear which optimally requires girth adjustability at the ball of the foot, where the MP (metatarsal/phalange) joints flex during the gait cycle. This, and similar approaches using air, gels, gas, plastic foam, and other mechanical means, while useful in rigid-soled footwear particularly when used rearward of the ball have generally been precluded from use at or over the ball, primarily for comfort and foot health considerations in this relatively sensitive and critical fitting area.